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Introduction

Today it is widely accepted that the Earth's crust consists of a series of huge plates that slowly move. The low parts of the plates are beneath the world's oceans, and the high parts of the plates are landmasses. New plate material is generated at deep sea ocean ridges in a process called sea-floor spreading. Material from plates is also recycled at trenches, where dense, oceanic crust dives back (subducts) underneath an adjacent plate towards the upper mantle. Figure 1 shows a map of the major tectonic plates.

The theory of plate tectonics revolutionized geology in the 1960s. Before this, geology had been a descriptive science. Mechanisms for large-scale processes such as the formation of mountain ranges were put down to vague "earth forces." Plate tectonics changed that. A series of scientific papers by Harry Hess, Robert Dietz, Fred Vine, Drummond Matthews, and others brought together a growing body of evidence that massive pieces of the earth's surface were constantly on the move. Subduction of one plate beneath another could provide the massive force to produce uplift of mountain ranges. Fifty years earlier, in 1912, Alfred Wegener had proposed his theory of continental drift, and was widely ridiculed. Wegener, like others before him, had noticed that the continents on either side of the Atlantic Ocean had complementary shapes, suggesting that they might have originated much earlier from the same landmass. He had also noted similarities in rock formations on opposite sides of the ocean, and similarities in both living and fossil animals. Wegener did not have a good explanation for how vast chunks of the earth's surface could move relative to one another, and the community of geologists was not ready to accept his ideas (McPhee, 1981-1998; WGBH, 1998).

Figure 1. Map of major tectonic plates of the earth. (Tilling, date unknown).

Today we still do not know the mechanism for the motion of the plates, although it is thought that convection of heat from the earth's interior is somehow involved. The evidence that clinched the case for plate tectonics came from detailed mapping studies of paleomagnetism. Rocks containing magnetic material reveal the history of when and where they were formed. As the molten rock cooled, the magnetic particles aligned themselves with the earth's magnetic field. Although the positions of the earth's magnetic poles have changed over the billions years of earth's history, geologists have been able to recreate the time line of those changes. Armed with that information, geologists have been able to map the dates of origin of the oceanic crust, and to confirm that sea-floor spreading at suboceanic ridges and subduction at trenches is a constant process.

How are earthquakes related to tectonic plates? The following paragraph from Annals of the Former World by John McPhee, summarizes the connection quite well (McPhee, 1981-1998, 121):

Almost all earthquakes are movements of the boundaries of plates—shallow earthquakes at the trailing edges, where the plates are separating and new material is coming in, shallow earthquakes along the sides, where one plate is ruggedly sliding past another (the San Andreas Fault), and earthquakes of any depth down to four hundred miles below and beyond the trenches where the plates are consumed (Japan, 1923; Chile, 1960; Alaska, 1964; Mexico, 1985).

The goal of this project is to collect historic earthquake data and map it. If the plate tectonics theory of earthquake activity is true, then the great majority of earthquake activity should occur at or near boundaries between tectonic plates. Do you think that historic earthquake data will support McPhee's statement?

Terms and Concepts

To do this project, you should do research that enables you to
understand the following terms and concepts:

This is a good, brief introduction to the structure of the Earth:Robertson, E.C., date unknown. "The Interior of the Earth," United States Geological Survey, General Interest Report [accessed January 30, 2007] http://pubs.usgs.gov/gip/interior/.

Here is an Excel tutorial to get you started using a spreadsheet program:
Excel Easy. (n.d.). Excel Easy: #1 Excel tutorial on the net. Retrieved June 12, 2014, from http://www.excel-easy.com/

Further reading. What could be more boring than reading about rocks? If you pick the right book, the geology of the Earth and the people who study it are downright fascinating. Here is an excellent and ambitious book on geology for the general reader by a masterful nonfiction writer, John McPhee (his set piece on plate tectonics runs from pages 115-131):
McPhee, J., 1981-1998. Annals of the Former World. New York, NY: Farrar, Strauss and Giroux.

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Materials and Equipment

To do this experiment you will need the following materials and equipment:

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Experimental Procedure

For each event, keep track of the following information in a table (or in a spreadsheet file):

Latitude

Longitude

Magnitude

Depth

The more events from which you collect data, the better.

Let's walk through an example so that you can see where to find the data you'll need.

The screenshot shows a portion of the list at the Historic Worldwide Earthquakes webpage. To get more information about a particular earthquake, click on the link. We're going to be looking at data from a magnitude 6.3 temblor with epicenter on Kyushu Island, Japan that occurred on June 11, 2006, at 20:01:29 UTC.

Clicking on the link for this quake brings us to a page with the information shown in the screenshot.

Copy the information you need for each earthquake (highlighted in yellow rectangles).

Notice that there are additional tabs (Summary, Maps, Scientific & Technical, highlighted in green rectangle) with additional information about each quake. You'll probably be interested in checking out the Summary and Maps tabs for each quake you study.

By default, the quakes on the Historic Worldwide Earthquakes page are sorted by date. At the top right of the page there are additional sorting options, as shown in the screenshot.

Using transparencies, map the collected earthquake data over the world map.

Think of ways to encode the earthquake data with your mapping symbols. For example, you could encode earthquake magnitude with the size of the symbols, and earthquake depth with the color of symbols.

Remember, correlation does not prove causation. A correlation of earthquake activity with known plate boundaries would provide supportive evidence for the plate tectonic theory. A lack of correlation would be significant evidence against the plate tectonic theory.

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Ask an Expert

The Ask an Expert Forum is intended to be a place where students can go to find answers to science questions that they have been unable to find using other resources. If you have specific questions about your science fair project or science fair, our team of volunteer scientists can help. Our Experts won't do the work for you, but they will make suggestions, offer guidance, and help you troubleshoot.

Related Links

If you like this project, you might enjoy exploring these related careers:

Geoscientist

Just as a doctor uses tools and techniques, like X-rays and stethoscopes, to look inside the human body, geoscientists explore deep inside a much bigger patient—planet Earth. Geoscientists seek to better understand our planet, and to discover natural resources, like water, minerals, and petroleum oil, which are used in everything from shoes, fabrics, roads, roofs, and lotions to fertilizers, food packaging, ink, and CD's. The work of geoscientists affects everyone and everything.
Read more

Remote Sensing Scientist or Technologist

Have you ever climbed up high in a tree and then looked at your surroundings? You can learn a lot about your neighborhood by looking down on it. You can see who has a garden, who has a pool, who needs to water their plants, and how your neighbors live. Remote sensing scientists or technologists do a similar thing, except on a larger scale. These professionals apply the principles and methods of remote sensing (using sensors) to analyze data and solve regional, national, and global problems in areas such as natural resource management, urban planning, and climate and weather prediction. Because remote sensing scientists or technologists use a variety of tools, including radio detection and ranging (radar) and light detection and ranging (lidar), to collect data and then store the data in databases, they must be familiar with several different kinds of technologies.
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Geographer

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Cartographer or Photogrammetrist

Maps can give us much more information than ways to get from A to B. Maps can give us topographic, climate, and even political information. Cartographers and photogrammetrists collect a vast amount of data, such as aerial data and survey data to produce accurate maps and models. For example, by collecting rainfall data, a cartographer can make an accurate model of how rainfall can affect an area's watershed. The maps and models can then be used by policy makers to make informed decisions.
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